“I need to see them crash.” These are the first fated words of a future filmmaker, Sammy Fabelman (Mateo Zoryon Francis-DeFord), whispered to his mother, Mitzi (Michelle Williams) after he’s crashed his toy train after bedtime, inspired by his very first big-screen cinematic experience, “The Greatest Show on Earth.” Mitzi instantly recognizes that re-creating the train crash is a way for young Sammy to exert some control over the fear he felt during the movie, and so she presents him with his father’s 8mm camera to capture, and replay, the crash. With this lesson on art as catharsis imprinted …